Linear motion guide unit having a reduced height

ABSTRACT

A linear motion guide unit including a bed, a sliding table and a plurality of rolling members interposed between the bed and the sliding table to provide a relative sliding motion therebetween. The bed has an outwardly extending mounting wall section and it is mounted on a housing having an associated recess or hole. Thus, when the linear motion guide unit is mounted in position, it is located in the associated recess or hole so that the overall exposed height of the present linear motion guide unit can be made extremely small, thereby allowing to be used in moving parts of various devices, such as floppy disc and hard disc drives.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a linear motion guide unit suitablefor use in moving parts of various machines and apparatuses, and, inparticular, to a height-reduced linear motion guide unit.

2. Description of the Prior Art

A typical example of a prior art linear motion guide unit for use inmoving parts of various devices is illustrated in FIG. 2 of JapanesePat. Laid-open Pub. No. 61-136018. However, as shown in FIG. 5 of thisapplication, this type of linear motion guide unit is fixedly mounted ona housing A of a device by tightely securing its bed B thereto using abolt C. The bed B has a generally U-shaped cross section and it ismounted on the housing A with its bottom wall portion in contact withthe housing A. A sliding table E also having a generally U-shaped crosssection is received in a space defined by the bed B, and a plurality ofrolling members D are interposed between the bed B and the sliding tableE so that the sliding table E can move relative to the bed B and thus tothe housing A along a straight path back and forth. Such a linear motionguide unit is commonly used in the moving parts of such devices asfloppy disc drives and hard disc drives.

The prior art linear motion guide units typically have a relativelylarge height H from a surface F of a housing A to a top surface G of asliding table, as indicated in FIG. 5, on the order of approximately 7mm at minimum. However, there has been a need to reduce the height ofsuch a linear motion guide unit, first, to allow a high degree offlexibility in the design of such devices as floppy disk drives and haddisc drives, and second to increase the scope of linear guide motionunit application, such as, for instance, use the high precisionmeasuring devices.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a linearmotion guide unit having a reduced height. The linear motion guide unitgenerally includes a bed, a sliding table and a plurality of rollingmembers, such as rollers and balls, interposed between the bed and thesliding table. The main feature of the present invention resides in thestructure of the bed. That is, in accordance with the present invention,the bed has a pair of guide wall sections extending generallyvertically, a connecting wall section connecting the pair of guide wallsections, and a plurality of mounting sections which extend generallyhorizontally from respective ones of the pair of guide wall sections ina direction away from the opposite guide wall sections. In the preferredembodiment, the bed is generally in the shape of a plate which is formedwith a window with its opposite sides bent upwardly to thereby definethe pair of guide wall sections. In this case, the plate section of thebed defines the connecting wall and mounting sections. Thus, a pluralityof mounting holes may be formed in the plate.

An outer guide groove is formed in each of the opposite surfaces of thepair of guide wall sections. An inner guide groove is formed in acorresponding outer surface of the sliding table. Thus, when assembled,paired outer and inner guide grooves define a guide channel, in which aplurality of rolling members may be provided. A retainer may also beprovided in the guide channel so as to keep the rolling members spacedapart each other in a predetermined manner, such as at a predeterminedpitch.

The present linear motion guide unit may be mounted on a housing havinga corresponding recess or a through-hole as being located therein atleast partly. Since the mounting sections extend generally horizontallyand outwardly in opposite directions from the pair of side wallsections, the linear motion guide unit may be located in thecorresponding recess or a hole at least partly. Therefore, the height ofthe linear motion guide unit can be minimized when mounted on anassociated housing.

It is therefore a primary object of the present invention to obviate thedisadvantages of the prior art as described above and to provide animproved linear motion guide unit having a significantly reduced height.

Another object of the present invention is to provide an improved linearmotion guide unit having a height measured from a surface of a housing,to which the present linear motion guide unit is attached, to a topsurface of its sliding table in a range between approximately 1.5 mm and5 mm.

A further object of the present invention is to provide an improvedlinear motion guide unit simple in structure, easy to manufacture andthus low in cost.

A still further object of the present invention is to provide animproved linear motion guide unit suitable for use in moving parts ofvarious small-sized devices, such as floppy disc drives, hard discdrives and high precision measuring devices.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing in transverse cross section alinear motion guide unit constructed in accordance with one embodimentof the present invention as mounted on an associated housing;

FIG. 2 is a schematic illustration showing in bottom with the linearmotion guide unit shown in FIG. 1;

FIGS. 3 and 4 are schematic illustrations showing in transverse crosssection alternative embodiments of the present invention as mounted onan associated housing; and

FIG. 5 is a schematic illustration showing in transverse cross section atypical prior art linear motion guide unit as mounted on an associatedhousing.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIGS. 1 and 2, there is schematically shown a linearmotion guide unit constructed in accordance with one embodiment of thepresent invention. As shown, the present linear motion guide unitgenerally includes a bed 1, a sliding table 4 and a plurality of rollingmembers 3, such as balls or rollers. The bed 1 has a pair of guide wallsections 2 which generally extend vertically, a pair of connecting wallsections which connect the pair of guide wall sections and a pair ofmounting sections 5 which extend generally horizontally outwardly fromthe respective guide wall sections 2. In the illustrated embodiment, thebed 1 is plate-shaped or generally in the shape of a picture frame. Thatis, a window is opened generally at the center of a rectangular plate,and the opposite side sections of the window are bent to define the pairof guide wall sections 2.

Each of the guide wall sections 2 has an inner guide surface which isformed with an outer guide groove. The sliding table 4 has a generallyU-shaped cross section and thus it has a flat top wall section and apair of vertical wall sections which extend vertically from therespective sides of the top wall section. An inner guide groove isformed at an outer guide surface of each of the vertical wall sections.Thus, when assembled, a guide channel is defined between opposed innerand outer guide grooves, in which the rolling members 3 are provided toprovide a rolling contact between the bed 1 and the sliding table 4. Aretainer for retaining the rolling members spaced apart in apredetermined fashion may also be provided. Thus, the sliding table 4may move relative to the bed 1 along a straight line back and forth asindicated by a double arrow X in FIG. 2.

In the case of the embodiment shown in FIGS. 1 and 2, the mountingsections 5 and connecting sections define a continuous frame or flange,and a plurality (four in the present embodiment) of mounting holes 7 areformed in the frame. A housing of a device to which the present linearmotion guide unit is to be mounted has a through-hole 9. Thus, when thepresent linear motion guide unit is mounted in position, its substantialportion is located inside the hole 9 preferably with an outer surface 10of each of the pair of guide wall sections 2 in contact with the edge ofthe hole 9. The mounting section or frame 5 is brought in contact with abottom surface 12 of the housing 6 so that the present linear motionguide unit may be set in position by threading bolts 7 into threadedholes 13.

In this embodiment, a substantial portion of the linear motion guideunit is located in the hole 9 of the housing 6, and, therefore, anexposed height H from a front surface 14 of the housing 6 to a topsurface 15 of the sliding table is extremely small and can be made onthe order of 3 mm. Moreover, since the linear motion guide unit isinserted into the hole of the housing, there is provided an enhancedstructural integrity between the present linear motion guide unit andthe housing 6. That is, when the guide wall sections 2 are in abutmentagainst the surfaces of the hole 9, the guide wall sections 2 cantolerate larger forces, so that the bed 1 can be made from a thinnersheet or plate of any desired material, such as a metal. This wouldcontribute to reduce the weight of the unit, which can be important insuch devices as floppy disc and hard disc drives.

It is to be noted that the rolling members 3 may be of any desired type,such as balls and rollers. In addition, although a limited stroke typelinear motion guide unit is illustrated in FIGS. 1 and 2, it may be ofan indefinite stroke type linear motion guide unit having a guidechannel in the form of an endless loop.

FIG. 3 illustrates another embodiment of the present invention. Thelinear motion guide unit of this embodiment generally includes a bed 16,a sliding table 21 and a plurality of rolling members interposed betweenthe bed 16 and the sliding table 21. This embodiment is similar in manyrespects to the previous embodiment shown in FIGS. 1 and 2. However, inthe present embodiment, mounting section or frame 17 of the bed 16 is incontact with a top surface 19 of a housing 18 rather than its bottomsurface. In addition, the bed 16 has a pair of guide wall sections 20which extend generally vertically and terminate at a lower height ascompared with the guide wall sections 2 of the previous embodiment. As aresult, bottom ends 22 of the sliding table 21 are located at a lowerposition and in the illustrated extend partly into the space defined bya through hole 23 formed in the housing 18. In this embodiment, anexposed height H between the top surface 19 of the housing 18 and thetop surface 24 of the sliding table 21 may be made as small asapproximately 5 mm.

FIG. 4 illustrates a further embodiment of the present invention. Thisembodiment includes a bed 25 having a pair of guide wall sections 26,which extend generally vertically downwardly, a sliding table 32 and aplurality of rolling members 33 interposed between the bed 25 and thesliding table 32. The bed 25 also has a mounting section or frame 27which extends generally horizontally and whose bottom surface 28 restson a top surface 30 of a housing 29 having a through-hole 31. In thisembodiment, a substantial portion of the linear motion guide unit islocated inside the through-hole 31 of the housing 29. Thus, an exposedheight H from the top surface 30 of the housing 29 to a top surface 34of the sliding table 32 can be made extremely small and on the order of1.5 mm-2 mm. In addition, as described with reference to the firstembodiment shown in FIGS. 1 and 2, since each of guide channels definedby inner and outer guide grooves formed in the opposed surfaces of thevertical wall sections of the bed 25 and the sliding table 32 is locatedin horizontal alignment with the housing 29, the guide channel is wellprotected against possible deformations due to application of undersiredforces. Thus, this embodiment also provides advantages of an enhancedstructural integrity as well as reduced exposed height.

It is to be noted that although all of the above-described embodimentsof the present invention has a bed generally in the shape of a pictureframe and such a picture frame type bed is a preferred embodiment, thepresent invention should not be limited only to such a specificstructure. That is, a bed may have various other shapes as long as itincludes at least one mounting section which extends outward from aguide wall section in a direction away from the opposite guide wallsection. Accordingly, the structure shown in FIG. 5 may be modified bycutting portions of the bottom wall section of the bed B and bending theportions thus cut to extend outward or in directions away from theopposite vertical wall sections. Such modifications should be covered bythe scope of the present invention. Thus, in accordance with the presentinvention, it is only required to provide a mounting section whichextends generally horizontally in an outward direction and which may beused to mount the linear motion guide unit on a desired object, such asa housing. It should also be noted that although a through-hole isformed in an associated housing in all of the above-describedembodiments, such a through-hole may be replaced by a recess formed inthe housing, if necessary.

While the above provides a full and complete disclosure of the preferredembodiments of the present invention, various modifications, alternateconstructions and equivalents may be employed without departing from thetrue spirit and scope of the invention. Therefore, the above descriptionand illustration should not be construed as limiting the scope of theinvention, which is defined by the appended claims.

What is claimed is:
 1. A linear motion guide unit comprising:a bedhaving a first guiding means, said bed being generally in the shape of apicture frame; p1 a sliding table having a second guiding means locatedopposite to and in parallel with said first guiding means whenassembled; and a plurality of rolling members interposed between saidfirst and second guiding means, thereby providing a sliding contactbetween said bed and said sliding table; whereby said bed includes: apair of guide wall sections formed with said first guiding means andspaced apart from each other over a predetermined distance, said guidewall sections extending generally vertically; at least one connectingwall section connecting said pair of guide wall section; and at leastone mounting wall section which extends generally horizontally from eachof said pair of guide wall sections in a direction away from theopposite guide wall section, thereby allowing said mounting wall sectionto be placed on a desired object to be mounted, wherein said object tobe mounted includes a recess or hole in which said unit is partlylocated.
 2. The unit of claim 1, wherein said rolling members arelocated in said recess or hole.
 3. The unit of claim 1, wherein said bedis generally in the shape of a rectangular plate formed with arectangular hole generally at its center, and said pair of guide wallsis formed on the opposite sides of said rectangular hole.
 4. The unit ofclaim 3, wherein said plate is formed with a plurality of mounting holesso that the plate may be bolted to said object to be mounted.